Method for error correction in synchronized superposed operation of servomotors

Abstract

In a method for performing a synchronized superposed operation of two servomotors, controllers for the servomotors perform the control for achieving the synchronized superposed operation by: calculating, for each of the servomotors, the difference, or differences, between the ideal speed and/or position deviations obtained from a control command and the actual speed and/or position deviations obtained from the rotation of the servomotor; calculating a speed correction quantity, or a speed correction quantity and a current correction quantity, from the discrepancy, or discrepancies, between the differences calculated for both of the servomotors; and adding the correction quantity, or quantities, to a speed command, or to a speed command and a current command, given to the subsidiary shaft side. Thus, a synchronized superposed operation of servomotors in which speeds and responses of the main shaft and the subsidiary shaft are well balanced therebetween can be achieved.

What is claimed is: 
     
       1. A method for error correction in a synchronized superposed operation of servomotors for rotating respective shafts coupled to said servomotors, comprising the steps of: obtaining an ideal position deviation of a main shaft based on a target position command for a controller of a servomotor coupled to said main shaft;   obtaining an actual position deviation of said main shaft based on an actual position of said main shaft;   calculating a difference between said ideal position deviation and said actual position deviation to thereby obtain a first position deviation difference;   obtaining an ideal position deviation of a subsidiary shaft based on a target position command for a controller of a servomotor coupled to said subsidiary shaft;   obtaining an actual position deviation of said subsidiary shaft based on an actual position of said subsidiary shaft;   calculating a difference between said ideal position deviation of said subsidiary shaft and said actual position deviation of said subsidiary shaft to thereby obtain a second position deviation difference;   calculating a speed correction quantity from a difference between said first position deviation difference and said second position deviation difference; and   correcting a speed command in said subsidiary shaft controller as a function of said speed correction quantity.   
     
     
       2. A method for error correction in a synchronized superposed operation of servomotors for rotating respective shafts coupled to said servomotors, comprising the steps of: obtaining an ideal position deviation of a main shaft based on a target position command for a controller of a servomotor coupled to said main shaft;   obtaining an actual position deviation of said main shaft based on an actual position of said main shaft;   obtaining an ideal speed deviation of said main shaft based on said target position command;   obtaining an actual speed deviation of said main shaft based on an actual speed of said main shaft;   calculating a difference between said ideal position deviation and said actual position deviation to thereby obtain a first position deviation difference;   calculating a difference between said ideal speed deviation and said actual speed deviation to thereby obtain a first speed deviation difference;   obtaining an ideal position deviation of a subsidiary shaft based on a target position command for a controller of a servomotor coupled to said subsidiary shaft;   obtaining an actual position deviation of said subsidiary shaft based on an actual position of said subsidiary shaft   obtaining an ideal speed deviation of said subsidiary shaft based on said target position command for said controller of a servomotor coupled to said subsidiary shaft;   obtaining an actual speed deviation of said subsidiary shaft based on an actual speed of said subsidiary shaft;   calculating a difference between said ideal position deviation of said subsidiary shaft and said actual position deviation of said subsidiary shaft to thereby obtain a second position deviation difference;   calculating a difference between said ideal speed deviation of said subsidiary shaft and said actual speed deviation of said subsidiary shaft to thereby obtain a second speed deviation difference;   calculating a speed correction quantity from a difference between said first position deviation difference and said second position deviation difference;   calculating a current correction quantity from a difference between said first speed deviation difference and said second speed deviation difference;   correcting a speed command in said subsidiary shaft controller as a function of said speed correction quantity; and   correcting a current command in said subsidiary shaft controller as a function of said current correction quantity.